Amplifier movements for use with pressure gauges, temperature gauges or the like are well known and have been used commercially for many years. Typically, such gauges have a condition responsive element such as a bellows, Bourdon tube, bi-metal coil or the like providing selected displacement motion in response to condition changes to which the element is sensitive and exposed. In a common construction, the amplifier or "movement" is comprised of leverage and gearing operably responsive to displacement motion of the condition responsive element for driving an output shaft supporting a pointer movable relative to a fixed dial plate. The dial registration opposite the pointer position is indicative of the condition state such as pressure or temperature with which the instrument is being operative.
Disclosed in U.S. Pat. No. 4,055,085 to R. H. Wetterhorn is a pressure gauge in which the amplifier is supported on the free end of a Bourdon tube for floating conjoint movement with displacement of the tube. A remotely connected actuator extending into the motion path of the floating amplifier defines a pivot axis for a hinged gear sector arm thereof. In pivotting about the actuator axis, the sector arm operably drives a rotatable output shaft supporting the pointer. In a typical production manufacture of such gauges, a clip of sorts has been utilized for securing or connecting the amplifier onto the tube end.
Accuracy of such gauges is, of course, a key criteria in the manufacture and marketing thereof and as described in the above Wetterhorn patent, the geometries and interrelationships of the working components of a floating movement are critical if the desired level of operational accuracy is to be maintained. For this reason, manufacturing tolerances of these components have been carefully controlled to ensure these interrelationships. Notwithstanding, it has only recently been realized that minor deviations in the mechanical spring properties of the Bourdon tube can per se cause sufficient differences in residual recovery from its coiling formation that its post-formed tip orientation can vary significantly from tube to tube. In practice, its has been found that Bourdon tube tip orientation can vary vertically from its intended or ideal location about plus or minus 0.050 inches and which variation effects non-linearity of the gauge on the order of up to about five percent. Despite recognition of the foregoing, a ready solution has not heretofore been known.